When developing drive units for vehicles, attempts are constantly being made to minimize fuel consumption. The aim is moreover to reduce pollutant emissions so that it is possible to observe future limit values for pollutant emissions. Therefore, according to the prior art, an electric drive is used more and more frequently in vehicles—generally in combination with an internal combustion engine as a hybrid drive.
In terms of lowering fuel consumption or reducing pollutant emissions, this is only advantageous if the electric drive has a greater efficiency in at least one operating range or engine map range than the internal combustion engine and therefore an advantage over the internal combustion engine, or if the drive energy necessary for the electric drive comes from energy recovery on board the vehicle or has been generated by regenerative, i.e. renewable, energy sources. Irrespective of this, the electric drive has its merits and advantages as an emission-free drive in inner-city traffic.
However, there are further relevant reasons for using electric drives, for example the reduction in the drive noise of a vehicle. The noise emissions of a motor vehicle, in particular the drive noises, not only have a disadvantageous effect on the quality of life or the wellbeing of people exposed to the noise, but also on their health, which is why a multitude of regulations have been established which stipulate the noise limit values to be observed. In this case, the most important regulations are the Federal Emission Control Act (BImSchG) and the guidelines of the European Commission.
However, the lack of drive noise of an electric drive also has disadvantages. If the electric machine is used as a drive unit in the two-pedal mode, the driver, owing to the lack of combustion noise from the internal combustion engine, is uncertain and uninformed as to whether and when it is necessary or advisable to shift transmission gears, i.e. when the gear should—preferably—be changed by manually shifting the transmission. Electric machine map-optimized operation of the electric machine is therefore random rather than achievable in an appropriately targeted manner. As a result, the potential offered by a hybrid drive remains at least periodically and at least partially unused.
Against the background of the above, it is the object of the present description to demonstrate a method for operating a drive unit as described herein, with which the operation and the control of the drive unit in the two-pedal mode, in which the electric machine is used as the drive unit, is improved.
Accordingly, the description relates to a method for operating a drive unit comprising an internal combustion engine, which is at least drive-connectable to an electric machine which delivers power to a drivetrain or receives power, and comprising at least one automatically actuable clutch, wherein the electric machine is at least drive-connectable to a manually shiftable transmission of the drive train, the transmission comprises a plurality of gears with which different transmission ratios can be realized, in a two-pedal mode, in which the electric machine is used as a drive unit, the transmission is manually shiftable without actuation of a clutch, and in a three-pedal mode, in which the internal combustion engine is used as a drive unit, the transmission is manually shiftable with actuation of a clutch.
The description furthermore relates to a drive unit for carrying out a method of the type mentioned above. A further partial object of the present description is to provide a drive unit for carrying out a method of this type. A drive unit of the type mentioned at the outset is used for example as a motor vehicle drive. Within the framework of the present description, the term internal combustion engine comprises diesel engines and gasoline engines, but also hybrid internal combustion engines which use a hybrid combustion method.
A drive unit comprising an internal combustion engine and an electric machine is generally also referred to as a hybrid drive. In the present case, as a drive unit for driving a vehicle, it is possible to use the electric machine exclusively in a two-pedal mode and the internal combustion engine exclusively in a three-pedal mode. However, it is also possible to use and operate the electric machine as a drive simultaneously along with the internal combustion engine. Both the internal combustion engine and the electric machine then deliver power to the drive train.
The present description may provide several advantages. In particular, the approach may improve drivetrain efficiency. Further, the approach may improve ease of driving a vehicle. Additionally, the approach may improve a human driver's confidence of operating a manual transmission.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.